1. Field of the Invention
The invention concerns an autonomous radio timepiece wherein a time display, maintained by an autonomous internal time keeping circuit, is corrected by radio transmitted, absolute time information.
2. Description of Related Art
A radio timepiece is known for example from U.S. Pat. No. 4,650,344 issued to Allgaier et al on Mar. 17, 1987, herein incorporated by reference. The radio timepiece disclosed in this patent includes an electro-mechanical time display wherein, for example, the angular positions of hands are based on the stepping movement provided by an internal time keeping circuit. In operation, the patented radio timepiece determines from time to time whether the instantaneous electro-mechanical time display coincides with the prevailing absolute time. The absolute time is emitted in coded form by a transmitter separate from the timepiece and decoded by a receiver, which is built into the timepiece and tuned to said transmitter. If necessary, the time display is corrected on the basis of the complete, decoded absolute time information received. In order to be able to determine whether any display correction may be expected (upon the activation of the timepiece, i.e., in case of a randomly incorrect display, or following the actuation of the so-called "transmitter call button") by means of received radio information, an indicator hand is provided on each radio timepiece. The indicator hand is stepped forward initially at the cycle time of the coding frequency received, until absolute time information has been decoded for the correction of the time display. Any irregular motion of the indicator hand is an unerring indication of the fact that no undisturbed reception of the time information coded in seconds rhythm is possible and that therefore no setting or correction of the time display is to be expected under the prevailing receiving conditions. This is correspondingly true if, following a reset, the seconds information received and decoded is displayed digitally but is not counted up from 1 to 59 without interference in the seconds rhythm.
It is known from DE-OS 37 31 956 to indicate by means of at least one electro-optical display the number of unsuccessful receiver actuations (decoding attempts) already performed. If these indications appear, for example, during the autonomous operation of the radio timepiece in the programmed hourly rhythm, the display provides information relative to the number of hours during which it has not been possible to monitor and eventually correct the prevailing time display by means of received absolute time information.
However, for small portable timepieces in particular, such as travel alarms or wrist watches, it is of special interest to be able to estimate whether under the prevailing operating conditions a reception of decodable automatic absolute time information may be expected at all, or whether the manual actuation of the receiver would be futile. This is so even if no indicator hand stepping in the seconds rhythm is available and without interrupting the autonomously advancing time display.